Method and device for melt spinning and cooling a plurality of monofilaments

ABSTRACT

The invention relates to a method and a device for melt spinning and cooling a plurality of monofilaments which are extruded through a plurality of openings of a spinneret and guided into a cooling bath. The removal process consists of redirecting the monofilaments within the cooling bath. According to the invention, in order to prevent adhesion and an oblique pull-off, the monofilaments are divided into multiple filament groups after extrusion, said groups consisting of multiple monofilaments, and the filament groups are individually redirected independently of each other within the cooling bath into multiple redirecting positions by separate redirecting sheaves.

The invention relates to a method for melt spinning and cooling a plurality of monofilaments according to the preamble of claim 1 as well as a device for melt spinning and cooling a plurality of monofilaments according to the preamble of claim 7.

In the production of monofilaments from a thermoplastic material it is common that for cooling purposes after extrusion the monofilaments are immediately guided into a cooling bath filled with water. This way, even in larger filament titers, short cooling paths can be realized in the melt spinning process. Inside the cooling bath, it is required to guide the monofilaments out of the cooling bath for further processing, particularly for stretching. For this purpose the monofilaments are redirected by at least one deflection means for pull-out of the cooling bath. Here, it is required that the monofilaments extruded through the jet openings at the bottom of the spinneret are jointly guided to a deflection means, for example, a deflection rod or a deflection roll. For this purpose, all extruded monofilaments are guided to a deflection position of the deflection means, at which they are jointly tangentially guided next to each other.

Such a method and a respective device are known, for example from DE 196 00 090 A1.

From the known method and the known device, several deflection means are arranged successively in the traveling direction of the filaments in the cooling path, in order to yield a redirection of the monofilaments as gently as possible. Here, after extrusion the monofilaments are all jointly guided to a first deflection position of the first deflection means. Depending on the distance between the spinneret and the deflection means here, greater redirections of the monofilaments that are extruded at the edge section of the spinneret are unavoidable. Such an oblique distortion at the monofilaments causes different tensions, which in turn result in different crystallization of the fibrous materials and in quality differences in the monofilaments. Additionally, in a large number of monofilaments the risk of contacting is increased when the monofilaments are joined at the deflection position, so that adhesions of individual monofilaments are unavoidable. Such problems particularly occur when melt spinning monofilaments are exclusively cooled by a cooling liquid in a cooling bath. In such methods and devices particularly, very short distances must be bridged between the spinneret and the deflection means inside the cooling bath.

Therefore the objective of the invention is to provide a method and a device for melt spinning and cooling a plurality of monofilaments of a generic type such that a large number of monofilaments can be extruded and cooled under conditions as homogenous as possible.

The objective is attained according to the invention for a method for melt spinning and cooling a plurality of monofilaments such that the monofilaments are divided after the extrusion into several filament groups comprising several monofilaments and that the filament groups are redirected individually and independently of each other inside the cooling bath at several deflection positions.

The solution by the device according to the invention is given such that the deflection means are arranged underneath the spinneret such that the monofilaments can be divided after extrusion into several filament groups comprising multiple monofilaments and that the filament groups are redirected independent from each other inside the cooling bath at several deflection positions.

Advantageous further embodiments of the invention are defined by the features and feature combinations of the respective dependent claims.

The invention allows for the monofilaments essentially being pulled off straight in the area between the spinneret and the deflection means. The deflection positions inside the cooling bath may be adjusted each to the monofilaments of the filament group and the position of the respective nozzle openings for extruding at a spinneret. The adjustment of the relative positions of the nozzle openings to the spinneret and the deflection position in the cooling bath in reference to each other allow for the monofilaments to be homogenously pulled off the spinneret. Additionally it is achieved here that each of the monofilaments travels over an equally long cooling distance of environmental air until reaching the cooling liquid.

In order to minimize the friction acting during the redirection of the filament groups at the monofilaments, it is provided according to an advantageous further development of the invention that the filament groups are redirected at each of the deflection positions by individual, freely rotating deflection rolls. For this purpose, each of the deflection means is formed by a freely rotating deflection roll, so that the filament groups can be guided in the deflection positions in a low-friction manner even at redirection angles >90°.

In order to limit the number of deflection means required for redirecting a very large number of monofilaments, the further development of the invention is particularly beneficial in which after extrusion the monofilaments are guided within their filament group between the spinneret and the deflection position with a maximal redirection of >5°. For this purpose, in the device according to the invention the positions and/or the number of deflection means underneath the spinneret are selected such that the monofilaments when pulled off the spinneret avoid a redirection angle >5°.

In general, the positions and the number of deflection means can be adjusted to the respective position and arrangement of the nozzle openings at the bottom of the spinneret. However, the monofilaments are preferably extruded next to each other in an annular arrangement, with the separation of the filament groups advantageously also occurring within the annular arrangement. For this purpose, the deflection means are preferably positioned underneath the spinneret in an arrangement congruent to the formation of the filament groups in reference to the nozzle openings of the spinneret.

Depending on the filament titer of the monofilaments and depending on the polymer material, it is necessary to allow differently long cooling paths. This can be realized advantageously in a further development of the invention, in which the deflection positions of the filament groups are embodied in an adjustable fashion. For this purpose the deflection means are preferably arranged at a plate-shaped fastener, which is embodied mobile to adjust the deflection positions.

In this way, pulling the monofilaments off the cooling bath can preferably be improved such that the fastener is connected to a carrier by a pivotal axis, by which an angle of inclination can be adjusted at the fastener. This way, height-adjusted deflection positions develop so that the monofilaments can be directly guided out of the cooling bath without any additional redirection.

The cooling path for cooling the monofilaments is preferably embodied by a height adjustment of the fastener. Here, the deflection positions inside the cooling bath can be adjusted in order to shorten or lengthen the cooling path.

In the following, additional advantages of the method according to the invention are described based on the exemplary embodiments of the device according to the invention with reference to the attached figures.

They show:

FIG. 1 schematically, a side view of a first exemplary embodiment,

FIG. 2 schematically, a top view of the exemplary embodiment of FIG. 1,

FIG. 3 schematically, another exemplary embodiment of a cooling bath with integrated deflection means,

FIG. 4.1

and

FIG. 4.2 various views of the deflection means of the exemplary embodiment of FIG. 3,

FIG. 5 schematically, a cross-section of another exemplary embodiment of the device according to the invention for performing the method according to the invention.

FIGS. 1 and 2 show a first exemplary embodiment of the device according to the invention to perform the method according to the invention in several views. FIG. 1 shows the exemplary embodiment schematically in a side view and in FIG. 2 the exemplary embodiment is shown in a top view without any spinneret. If no explicit reference is made to the figures, the following description applies to both figures.

For melt spinning and cooling a plurality of monofilaments, the exemplary embodiment comprises a spinneret 1, which is connected via a melt supply 3 to an extruder 2. The spinneret 1 comprises at its bottom a plurality of nozzle openings 4 (here, only one nozzle opening is shown in a partial cross-section). Underneath the spinneret 1 a cooling bath 5 is arranged, which is filled with a cooling liquid 6, preferably with water. Inside the cooling bath 5, several deflection means 7 are arranged at a distance from each other in the vertical direction underneath the spinneret. The deflection means 7 are provided in a congruent arrangement in reference to the nozzle openings 4 at the bottom of the spinneret 1 such that the monofilaments extruded from the nozzle openings 4 of the spinneret 1 can be guided to a deflection means 7 as a filament group 14 comprising several monofilaments in a path as straight as possible. In this example, the nozzle openings are embodied in an annular arrangement at the bottom of the spinneret 1. As discernible from the illustration in FIG. 2, accordingly the deflection means are also positioned in an annular arrangement in the cooling bath 5. The deflection means 7 are held off-set in their height in reference to each other inside the cooling bath 5, so that the filament groups 14 after redirection at the deflection means 7 can be jointly guided out of the cooling bath 5 in a diagonal thread progression.

At the outlet side of the cooling bath 5, a comb-shaped guide bar 12 is arranged, performing a separation of the monofilaments of the filament group 14 so that after leaving the cooling bath the filaments can be guided as assemblages 15.

A suction device 10 and a pull-off means 8 are arranged downstream in reference to the cooling bath 5. The suction device 10 comprises several suction nozzles 11 in order to suction off any cooling liquid adhering to the monofilaments.

The pull-off means 8 comprises several projecting godets 9, which are driven at a circumferential speed required for pulling off the monofilaments. In this exemplary embodiment, the pull-off means 8 are embodied with a total of four godets 9, with the filament assemblages 15 being guided at their circumference in a simple loop.

In order to perform the method according to the invention, a granulate of a thermoplastic material is added to the extruder 2 of the device according to the invention. For example polypropylene, polyamide, or polyester may be used as thermoplastic materials. After melting the granulate inside the extruder 2, the melt of the thermoplastic material is fed under pressure to the spinneret nozzle 1. At the bottom of the spinneret 1 the melt is extruded through the nozzle openings 4 into a plurality of monofilaments 13. The monofilaments 13 are directly extruded into the cooling liquid 6 of the cooling bath 5. In order to guide the monofilaments 13, several deflection means 7 are provided inside the cooling bath 5, so that after extrusion the monofilaments 13 each are divided into several filament groups 14 comprising several monofilaments each and the filament groups 14, independent from each other, being individually redirected inside the cooling bath 5 into several deflection positions determined by the deflection means 7. Here, the monofilaments 13 are essentially guided between the spinneret 1 and the deflection means 7 in a straight thread projection without essential redirections. This way, particularly the entering of the monofilaments 13 into the cooling liquid 6 can be performed under identical conditions for all monofilaments. Therefore, even a high number of monofilaments 13 can be cooled essentially without any different oblique distortion. This results in a high material homogeneity of all monofilaments.

After each of the filament groups 14 has been independently redirected by the separate deflection means 7, all monofilaments 13 are separated after being pulled out of the cooling bath 5 by the comb-shaped guide bar 12 so that for the further progression for thermal treatment and stretching of the monofilaments a parallel guiding of the monofilaments 13 is possible within the filament assemblages 15.

In the exemplary embodiment of the device according to the invention shown in FIGS. 1 and 2, the redirection of the filament groups occurs in the deflection positions preferably by freely rotating deflection rolls so that a low-friction guidance of the monofilaments is possible. However, alternative deflection means can also be used, such as rods or pins, for example, depending on the material selected for the monofilaments.

When pulling off the monofilaments in several filament groups, it has shown that for upholding a quality for all monofilaments as homogenous as possible, the redirection of the monofilaments during extrusion and entering into the cooling liquid shall be maintained at a redirection angle <5°, if possible. Here, the deviation between the thread guidance and a central axis extending vertically in reference to a nozzle opening shall be considered the deflection angle. For example, in a one-row annular arrangement of the nozzle openings 4 at the bottom of the spinneret 1, the deflection means 7 is positioned in a central axis of a nozzle opening 4. The nozzle openings 4 adjacent at both sides of the nozzle opening 4 may be allocated to the same deflection means 7 so that the monofilaments 13 extruded from the three nozzle openings jointly form the filament group 14 allocated to the deflection means 7.

In order to allow designing the deflection positions inside the cooling bath 5 as flexible as possible, another exemplary embodiment for fixing and arranging the deflection means 7 in a cooling bath 5 is shown in FIG. 3. In this exemplary embodiment, the deflection means 7 are formed by freely rotating deflection rolls 20. The deflection rolls 20 are arranged at a plate-shaped fastener 16. The fastener 16 is fastened to a carrier 17. The carrier 17 is held via a base plate 24 directly at the bottom of the cooling bath 5.

In order to explain the adjustment options of the deflection rolls and thus the deflection positions determined for adjustment, reference is additionally made to FIGS. 4.1 and 4.2. FIG. 4.1 schematically shows the fastener 16 fastened at the carrier 17 in a perspective view, and FIG. 4.2 shows the same in a schematic top view. The plate-shaped fastener 16 comprises a central fixing opening 18 with a fixing collar 19 extending parallel in reference to the carrier 17. The fixing collar 19 is connected via a pivotal axis 21 and a fixing screw 22 to the carrier 17. The fixing screw 22 is inserted into a guide slot 23 of the fixing collar 19 so that by way of loosening the fixing screw 22 the fixing collar 19 and thus the fastener 16 can be pivoted into an arbitrary incline. This way, the deflection rolls 20 held at the fastener 16 can be positioned inside the cooling bath at different heights in reference to each other by the incline of the fastener 16.

In order to adjust the height of the fastener 16 the pivotal axis 21 can be arranged between the fixing collar 19 and the carrier 17 at different positions at the fastener 17. For this purpose, the fastener 17 comprises several openings to accept the pivotal axis 21.

In order to yield a redirection of the filament groups in the same direction at the deflection rolls 20 held in an annular arrangement, the fastener 16 comprises two recesses 25.1 and 25.2 so that the deflection rolls 20 facing the recesses 25.1 and 25.2 of the fasteners 16 are enwrapped in the same direction in reference to the opposite deflection rolls 20 at the edge of the fastener 16.

The exemplary embodiment shown in FIGS. 3, 4.1 and 4.2, to arrange the deflection means inside the cooling bath is only one potential variant of an embodiment, though. FIG. 5 schematically shows in a cross-section another exemplary embodiment of the device according to the invention for performing the method according to the invention. In this exemplary embodiment, a support 26 is held at the bottom of the spinneret 1 in the center of the spinneret 1, projecting with its free end into the cooling bath 5. At the free end of the support 26 a plurality of support arms 27 is arranged spreading apart, which at their ends each carry a deflection means 7. At each deflection means 7, for example a deflection roll, here a filament group 14 with essentially straightly guided monofilaments 13 can each be redirected inside the cooling bath 5. The filament groups 14 are deflected separated from each other by deflection means 7 held at the ends of the support arms 27 and jointly guided to a guide roll 29 arranged in the cooling bath 5. Via the guide roll 29, the monofilaments 13 are pulled off the cooling bath 5 in the form of assemblages 15 and separated by a guide bar 12 arranged at the outlet side of the cooling bath 5. This exemplary embodiment is particularly suitable for spinneret 1 with an annular arrangement of the nozzle openings 4. The support 26 fastened at the bottom of the spinneret 1 may be embodied for example by a telescopic variant of the embodiment such that the deflection means 7 for adjusting the deflection position can be adjustable in their height. Additionally, the support arms 27 can be arranged at a head piece embodied pivotal in reference to the support 26. Here, the monofilaments may directly and diagonally be pulled off the cooling bath 5, too.

The method according to the invention and the device according to the invention are therefore particularly suitable to produce a plurality of monofilaments with a homogenous quality. Additionally, here the handling as well as the processing safety can be improved for the guidance of the monofilaments through the cooling liquid. By adjusting the height and the angle of the deflection means in reference to each other, the processing time inside the cooling bath can be changed and adjusted depending on the material of the monofilaments.

List of Reference Characters

-   1 spinneret -   2 extruder -   3 melt supply -   4 nozzle opening -   5 cooling bath -   6 cooling liquid -   7 deflection means -   8 pull-out means -   9 godets -   10 pull-out device -   11 suction nozzle -   12 guide bar -   13 monofilament -   14 filament group -   15 assemblages of monofilaments -   16 fastener -   17 carrier -   18 fixing opening -   19 fixing collar -   20 deflection roll -   21 pivoting axis -   22 fixing screw -   23 guide slot -   24 base plate -   25.1, 25.2 recess -   26 support -   27 carrier arm -   29 guide roll 

1-14. (canceled)
 15. A method for melt spinning and cooling a plurality of monofilaments, said method comprising: extruding the monofilaments through a plurality of nozzle openings of a spinneret and guiding the monofilaments into a cooling bath, in which the monofilaments when they are pulled off the cooling bath are guided by deflection means, wherein upon extrusion, the monofilaments are divided into several filament groups of several monofilaments and wherein the filament groups, independently of each other, are separately redirected inside the cooling bath into several deflection positions.
 16. The method according to claim 15, wherein the filament groups are each redirected in the deflection positions by individually freely rotating deflection rolls.
 17. The method according to claim 15, wherein upon extrusion, the monofilaments inside their filament group are guided between the spinning nozzle and the deflection positions with a maximal deflection <5°.
 18. The method according to claim 15, wherein the monofilaments are extruded next to each other in an annular arrangement and are divided into filament groups.
 19. The method according to claim 15, wherein a cooling path of the monofilaments inside the cooling bath is controlled by adjusting the deflection positions of the filament groups.
 20. The method according to claim 15, wherein upon cooling and redirection, the monofilaments of the filament groups are jointly guided as an assemblage, with the deflection positions inside the cooling bath partially being held at different heights.
 21. A device for melt spinning and cooling a plurality of monofilaments with a spinneret, said device comprising: a multitude of nozzle openings for extruding the monofilaments and arranged above a cooling bath; several deflection means for redirecting the monofilaments inside the cooling bath; and a pull-out means for pulling the monofilaments out of the cooling bath, wherein the deflection means are arranged underneath the spinneret such that, upon extrusion, the monofilaments can be divided into several filament groups of several monofilaments and wherein the filament groups can individually be redirected independent from each other inside the cooling bath at several deflection positions by the deflection means.
 22. The device according to claim 21, wherein the deflection means are formed by several freely rotating deflection rolls which are held individually in the deflection positions.
 23. The device according to claim 21, wherein the positions or the number of deflection means underneath the spinneret are selected such that, upon extrusion, the monofilaments inside their filament group can be guided between the spinneret and the deflection means with a maximum deflection of <5°.
 24. The device according to claim 21, wherein the nozzle openings of the spinneret are embodied in an annular arrangement at the bottom of the spinneret and wherein the deflection means are positioned underneath the spinneret in an arrangement congruent to form the filament groups.
 25. The device according to claim 21, wherein the deflection means are arranged at a distance in reference to a plate-shaped fastener, the fastener being embodied mobile in order to adjust the deflection positions.
 26. The device according to claim 25, wherein the fastener is connected via a pivotal axis to a carrier, by which an angular incline can be adjusted at the fastener.
 27. The device according to claim 25, wherein the fastener is connected to a carrier in a height-adjustable fashion.
 28. The device according to claim 21, wherein a comb-shaped guide bar is arranged downstream in reference to the deflection means outside the cooling bath, by which the monofilaments of the filament groups can be guided as an assemblage of separated monofilaments. 